U.S. patent application number 10/478136 was filed with the patent office on 2004-08-05 for magnetic sensor and method for manufacturing the same.
Invention is credited to Kuroe, Akio, Muramatsu, Sayuri, Murata, Akio, Takahashi, Ken, Tosaki, Yoshihiro.
Application Number | 20040150397 10/478136 |
Document ID | / |
Family ID | 19054213 |
Filed Date | 2004-08-05 |
United States Patent
Application |
20040150397 |
Kind Code |
A1 |
Kuroe, Akio ; et
al. |
August 5, 2004 |
Magnetic sensor and method for manufacturing the same
Abstract
In order to obtain a magneto-impedance type magnetic sensor
having a soft magnetic film facing to a conductive nonmagnetic
film, and available a large impedance change with a carrier signal
at a relatively low frequency, the magnetic sensor comprises a
meander type conductive nonmagnetic thin film of zigzag shape
formed with at least one pair of electrode terminals at both ends
and a soft magnetic film which is strip-shaped so as to face
thereto at a plurality of regions and has an easy axis of
magnetization in a width direction of the strip shape, a high
frequency carrier signal is applied to the above-mentioned
electrode terminals and further a direct current bias magnetic
field is applied. By performing AM detection of an AM modulation
signal output from the above-mentioned electrode terminals, an
impedance change of the conductive nonmagnetic film which is
changed by external magnetic field is detected as a change of the
high frequency carrier signal, thereby the external magnetic field
can be detected.
Inventors: |
Kuroe, Akio; (Katano-shi,
JP) ; Muramatsu, Sayuri; (Hirakata-shi, JP) ;
Murata, Akio; (Nara-shi, JP) ; Takahashi, Ken;
(Osaka-shi, JP) ; Tosaki, Yoshihiro; (Ibaraki-shi,
JP) |
Correspondence
Address: |
AKIN GUMP STRAUSS HAUER & FELD L.L.P.
ONE COMMERCE SQUARE
2005 MARKET STREET, SUITE 2200
PHILADELPHIA
PA
19103-7013
US
|
Family ID: |
19054213 |
Appl. No.: |
10/478136 |
Filed: |
November 20, 2003 |
PCT Filed: |
July 15, 2002 |
PCT NO: |
PCT/JP02/07188 |
Current U.S.
Class: |
324/249 ;
29/592.1; 324/252; 428/815; G9B/5.106 |
Current CPC
Class: |
G01R 33/02 20130101;
Y10T 428/1171 20150115; Y10T 29/49002 20150115; G11B 5/335
20130101; G11B 5/332 20130101 |
Class at
Publication: |
324/249 ;
324/252; 428/692; 029/592.1 |
International
Class: |
G01R 033/02; H01L
043/00; G11B 005/33 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2001 |
JP |
2001-220391 |
Claims
1. A magnetic sensor comprising: a soft magnetic film having an
easy axis of magnetization in a predetermined direction along with
the film face, a strip-shaped conductive nonmagnetic film provided
in zigzag on said soft magnetic film in a manner of being separated
from said soft magnetic film by an electric insulator, wherein the
length of a part parallel to the easy axis of magnetization of said
soft magnetic film is made longer than the length of a part
orthogonal to said easy axis of magnetization, a high frequency
power source for causing a high frequency current to flow through
said conductive nonmagnetic film, and a detection circuit for
detecting an external magnetic field on the basis of an impedance
change by said external magnetic field in said conductive
nonmagnetic film through which said high frequency current
flows.
2. A magnetic sensor comprising: a strip-shaped soft magnetic film
having an easy axis of magnetization in the direction perpendicular
to the longitudinal direction of the strip-shaped film and along
with the film face, a strip-shaped conductive nonmagnetic film
provided in zigzag on said soft magnetic film with an electrical
insulator therebetween, wherein the length of a part parallel to
the easy axis of magnetization of the film is made longer than the
length of a part orthogonal to said easy axis of magnetization in
the plane of said soft magnetic film, a high frequency power source
for causing a high frequency current to flow through said
conductive nonmagnetic film, and a detection circuit for detecting
an external magnetic field on the basis of the impedance change by
said external magnetic filed in said conductive nonmagnetic film
through which said high frequency current flows.
3. A magnetic sensor in accordance with claim 1 or 2 comprising a
conductive film for causing a direct current to flow to give a
direct current bias magnetic field to said soft magnetic film.
4. A magnetic sensor in accordance with claim 1 or 2 comprising a
permanent magnet for giving a direct current bias magnetic field to
said soft magnetic film.
5. A magnetic sensor in accordance with claim 1 or 2 comprising a
conductive film and a permanent magnet for flowing a direct current
to give a direct current bias magnetic field to said soft magnetic
film.
6. A magnetic sensor in accordance with claim 2 characterized in
that a plurality of said strip-shaped soft magnetic films are
arranged in parallel to each other.
7. A magnetic sensor in accordance with claim 2 characterized in
that said soft magnetic film comprises at least one slit which is
long in the direction perpendicular to the easy axis of
magnetization.
8. A magnetic sensor in accordance with claim 4 characterized in
that said permanent magnet is a magnet of thin film provided on
said conductive nonmagnetic film.
9. A magnetic sensor in accordance with claim 3, 4, 5 or 8
characterized in that the direction of said direct current bias
magnetic field is a direction orthogonal to the easy axis of
magnetization of said soft magnetic film.
10. A magnetic sensor in accordance with claim 1 or 2 characterized
in that said strip-shaped conductive nonmagnetic film is interposed
between at least two soft magnetic films with respective insulation
films therebetween.
11. A magnetic sensor in accordance with claim 10 characterized in
that at least two soft magnetic films interposing said conductive
nonmagnetic film contact with each other at a position remote from
said conductive nonmagnetic film.
12. A magnetic sensor in accordance with claim 10 characterized in
that a permanent magnet is provided between said at least two soft
magnetic films.
13. A magnetic sensor in accordance with claim 1 or 2 characterized
in that said soft magnetic film includes iron, tantalum and
nitrogen.
14. A magnetic sensor comprising: a soft magnetic film having an
easy axis of magnetization in a predetermined direction along with
the film face, formed on the principal face of a nonmagnetic
substrate, a strip-shaped conductive nonmagnetic film formed zigzag
on said soft magnetic film with an electrical insulation-film
therebetween, wherein the length of a part parallel to the easy
axis of magnetization of the film is made longer than the length of
a part orthogonal to said easy axis of magnetization in the plane
of said soft magnetic film, a conductive film for giving a direct
current bias magnetic field to said soft magnetic film by causing a
direct current to flow, formed on said conductive nonmagnetic film
with an insulation protection film therebetween, a high frequency
power source for causing a high frequency current to flow through
said conductive nonmagnetic film, and a detection circuit for
detecting an external magnetic field on the basis of the impedance
change by the external magnetic field in said conductive
nonmagnetic film through which said high frequency current
flows.
15. A magnetic sensor in accordance with claim 14 characterized in
that said soft magnetic film is a plurality of strip-shaped soft
magnetic films having the easy axis of magnetization in the
direction perpendicular to the longitudinal direction of the strip
shape and along with the film face.
16. A magnetic sensor in accordance with claim 14 characterized in
that said conductive film is provided between said nonmagnetic
substrate and said soft magnetic film.
17. A magnetic sensor in accordance with claim 14 characterized in
that a permanent magnet having magnet poles in the direction
perpendicular to said easy axis of magnetization is provided
between said nonmagnetic substrate and the soft magnetic film.
18. A magnetic sensor in accordance with claim 17 characterized in
that said permanent magnet is a magnet which is formed by
magnetizing a film of alloy including cobalt and platinum in the
direction perpendicular to said easy axis of magnetization.
19. A magnetic sensor in accordance with claim 14 characterized in
that the permanent magnet is formed by magnetizing a film of alloy
of cobalt and platinum provided on said strip-shaped conductive
nonmagnetic film in the direction perpendicular to said easy axis
of magnetization and along with the film face.
20. A magnetic sensor comprising: a strip-shaped first soft
magnetic film having an easy axis of magnetization in the direction
perpendicular to the longitudinal direction of the strip-shaped
film and along-with the film face, formed on a principal face of
a-nonmagnetic substrate, a strip-shaped conductive nonmagnetic film
formed zigzag on said soft magnetic film with a first insulation
film therebetween, wherein the length of a part parallel to the
easy axis of magnetization of the film is made longer than the
length of a part orthogonal to said easy axis of magnetization in
the plane of said soft magnetic film, a second soft magnetic film
having the easy axis of magnetization in the direction
perpendicular to the longitudinal direction of the strip shape and
along with the film face, formed on said conductive nonmagnetic
film with a second insulation film therebetween, a conductive film
for giving a direct current bias magnetic field to said soft
magnetic film by causing a direct current to flow, formed on said
second soft magnetic film with an insulation protection film
therebetween, a high frequency power source for causing a high
frequency current to flow through said conductive nonmagnetic film,
and a detection circuit for detecting said external magnetic field
on the basis of the impedance change by the external magnetic field
in said conductive nonmagnetic film through which said high
frequency current flows.
21. A magnetic sensor in accordance with claim 20 characterized in
that said first insulation film and second insulation film are
provided only on a circumference of said strip-shaped conductive
nonmagnetic film.
22. A magnetic sensor in accordance with claim 20 characterized in
that said (sic) permanent magnet is provided between the first soft
magnetic film and the conductive nonmagnetic film.
23. A magnetic sensor in accordance with claim 14 or 20
characterized in that said nonmagnetic substrate is a ceramic
including nickel oxide, titanium oxide and magnesium oxide.
24. A magnetic sensor having a closed magnetic path formed by soft
magnetic films, comprising: a conductive film for causing a direct
current to flow, provided so as to pass through the closed magnetic
path of said soft magnetic film, and a conductive nonmagnetic film
for causing a high frequency current to flow, provided so as to
pass through the closed magnetic path of said soft magnetic film
maintaining insulation on said conductive film.
25. A magnetic sensor in accordance with claim 24 characterized in
that the direct current bias magnetic field is given to said soft
magnetic film-by causing a direct current to flow through said
conductive film in a fixed direction.
26. A magnetic sensor in accordance with claim 24 comprising:
plural closed magnetic paths in said soft magnetic films, and
connection lines connecting respective conductive films passing
through each of said plural closed magnetic paths so that the
directions of the direct current flowing through the conductive
films in said respective closed magnetic paths become
identical.
27. A magnetic sensor in accordance with claim 26 characterized in
that said connection lines connecting said plural conductive films
are present outside of said closed magnetic paths.
28. A magnetic sensor in accordance with claim 26 wherein said
conductive nonmagnetic film is configured so as to pass through
plural closed magnetic paths of said soft magnetic films in the
opposite direction in sequence to respective longitudinal pattern
directions.
29. A magnetic sensor in accordance with claim 24 characterized in
that the conductive film and the conductive nonmagnetic film
passing through the closed magnetic paths of said soft magnetic
films are formed on the same plane parallel to the face of said
substrate.
30. A magnetic sensor in accordance with claim 24 characterized in
that patterns of plural soft magnetic films are arranged in
parallel.
31. A magnetic sensor in accordance with claim 24, wherein input
terminals of a high frequency amplifier are connected to both ends
of said conductive nonmagnetic film.
32. A fabrication method of a magnetic sensor comprising: step of
forming at least one strip-shaped first soft magnetic film on an
upper face of a nonmagnetic substrate, step of forming a conductive
film, a conductive first connection part and a second connection
part on said first soft magnetic film with a first insulation film
therebetween, step of forming a conductive nonmagnetic film on said
conductive film with a second insulation film therebetween, step of
forming a third insulation film on said conductive nonmagnetic
film, step of removing said first, second and third insulation
films on said first soft magnetic film so as to leave said first,
second and third insulation films in the vicinity including said
conductive film and conductive nonmagnetic film, step of forming a
closed magnetic path by forming a second soft magnetic film on said
first soft magnetic film and on said remaining first, second and
third insulation films, step of forming a fourth insulation film on
the entire face including said second soft magnetic film, step of
exposing said first and second connection parts by removing the
second, the third and the fourth insulation films on said first and
second connection parts and forming through holes, and step of
forming connection lines of electrical conductor to be electrically
connected to said first and second connection parts at both ends on
said fourth insulation film 94, respectively, and establishing
connection to the first conductive nonmagnetic film passing through
adjacent other closed magnetic path.
33. A fabrication method of a magnetic sensor in accordance with
claim 32 characterized in that said conductive film and conductive
nonmagnetic film are formed on the first insulation film in the
same process.
34. A fabrication method of a magnetic sensor in accordance with
claim 32 characterized in that a photoresist film of light
sensitive resin is used for at least one of said insulation
films.
35. A fabrication method of a magnetic sensor in accordance with
claim 32, wherein said first soft magnetic film is formed on said
nonmagnetic substrate with an insulation layer therebetween.
Description
TECHNICAL FIELD
[0001] The present invention relates to a high sensitivity magnetic
sensor for detecting an external magnetic field by impedance change
of a conductor due to a magnetism.
BACKGROUND ART
[0002] As a magnetic sensor for detecting a magnetism or a magnetic
field with a high sensitivity, a magneto-impedance element which
utilizes magneto-impedance effect is known. In the
magneto-impedance element, a constant current of a high frequency
is passed through a conductor provided adjacent to the magnetic
poles of a soft magnetic body. When the magneto-impedance element
is placed in a magnetic field, the impedance of the conductor is
changed by the magnetic field. A magnetism is detected on the basis
of the change of a high frequency voltage due to this change of the
impedance of the conductor.
[0003] Part (a) of FIG. 42 is a perspective view of a conventional
magneto-impedance element which is reported in the Electronics
Information Society Technical Report MR 95-80. Referring to the
figure, a detection conductor film 101 formed of a conductive metal
thin film is interposed between soft magnetic cores 105 and 106.
Each of the magnetic cores 105 and 106 is, as shown by a
cross-sectional view of part (b) of FIG. 42, a layered product of a
permalloy film 103 and a SiO.sub.2 film 104. A high frequency
current 109, which is a constant current of a UHF carrier signal,
is caused to flow through the detection conductor film 101 from a
high frequency generator 107 of UHF band via a resistor 108. A
voltage change based on the change of impedance due to the external
magnetic field shown by arrow 116 is detected across terminals 110
and 111 of conductive wires which are connected to respective ends
of the detection conductor film 101. A carrier signal voltage
corresponding to the product of a high frequency current 109 and
the impedance across the terminals 110 and 111 of the detection
conductor film 101 is generated across the terminals 110 and 111.
When an external magnetic field 116 exists, an orientation
direction of easy axis of magnetization of the soft magnetic cores
105, 106 oriented in the direction shown by an arrow 102 deviates
from the orientation direction due to the external magnetic field
116. As a result, the impedance of the detection conductor film 101
decreases in comparison with the case that no external magnetic
field exists. The decrease of the impedance is detected in the form
of an amplitude modulation signal of the carrier signal due to the
external magnetic field 116. The external magnetic field 116 can be
detected by carrying out AM detection to the amplitude modulation
signal. The magnetic sensor which utilizes the above-mentioned
magneto-impedance effect has a possibility of obtaining a detection
output as about ten times high as that of a giant
magneto-resistance element which is now in the process of
developing at present.
[0004] FIG. 43 shows a characteristic curve showing operation of
the magneto-impedance element shown in part (a) of FIG. 42, and
shows a relation of a magnetic field magnitude DC to a carrier
signal level. The frequency of the carrier signal is 1.0 GHz, and
the magneto-impedance element is placed in the central portion of
Helmholtz coils, and thereto a direct current (DC) magnetic field
is applied, and then the magnetic field magnitudes and a carrier
signal level are measured. In order to obtain a detection output
including a smaller amount of distortion with a high sensitivity,
as shown in FIG. 43, it is necessary to give a direct current bias
magnetic field of a magnetic field magnitude as shown by a straight
line 112.
[0005] The impedance of the magneto-impedance element is
proportional to the product of the frequency of the carrier signal
and a permeability. Therefore, in the case that the frequency is
high as mentioned above, a sufficient impedance change is
available. However, in the use for the magnetic sensor, there is a
case requiring use of a carrier signal of a relatively low
frequency. For example, in the case of detecting an external
magnetic field of a low level such as geomagnetism, it is required
to use a carrier signal of 10 MHz-20 MHz which is far lower than 1
GHz. Accordingly, a magneto-impedance element is demanded whereby a
sufficient impedance change is obtainable with a carrier signal of
such a relatively low frequency.
DISCLOSURE OF THE INVENTION
[0006] The present invention purposes to obtain a magnetic sensor
of a high sensitivity by realizing a magneto-impedance element in
which a high impedance change is attainable with a carrier signal
of a relatively low frequency.
[0007] The magnetic sensor of the present invention comprises a
soft magnetic film having an easy axis of magnetization in a
predetermined direction along with a film face, and a strip-shaped
conductive nonmagnetic film which is separated from the
above-mentioned soft magnetic film with an electric insulator and
is provided in zigzags thereon, wherein the length of a portion
parallel to the easy axis of magnetization of the above-mentioned
soft magnetic film is made longer than the length of a portion
orthogonal to the above-mentioned easy axis of magnetization. The
magnetic sensor further comprises a high frequency power source for
causing a high frequency current to flow through the
above-mentioned conductive nonmagnetic film, and a detection
circuit for detecting the above-mentioned external magnetic field
on the basis of an impedance change due to the external magnetic
field in the above-mentioned conductive nonmagnetic film through
which the above-mentioned high frequency current flows.
[0008] This magnetic sensor has an action and an effect as follows:
when a magnetic flux caused by the external magnetic field passes
the soft magnetic film in the direction perpendicular to the easy
axis of the magnetization (hard axis of magnetization), a
permeability of the soft magnetic film decreases at a portion
facing to the conductive nonmagnetic film. As a result, the
impedance of the conductive nonmagnetic film varies due to the
magneto-impedance effect. Since the variation of the impedance
corresponds to the magnitude of the external magnetic field, the
magnitude of the external magnetic field can be detected on the
basis of the variation of the impedance. The length of the part
parallel to the easy axis of magnetization of the soft magnetic
film of the zigzag conductive nonmagnetic film is made longer than
the length of the part orthogonal thereto. Therefore, there are
many regions on which the direction of the hard axis of
magnetization which is high in the permeability of the soft
magnetic-film is parallel to the direction of the magnetic flux
produced by the high frequency current flowing through the
conductive nonmagnetic film. For this reason, even in the case that
a high frequency carrier signal of a relatively low frequency is
used, the impedance value of the conductive nonmagnetic film can be
set to a large value, and hence the impedance change is large and
the external magnetic field is detected with a high
sensitivity.
[0009] A magnetic sensor in other aspect of the present invention
comprises a strip-shaped soft magnetic films having the easy axis
of magnetization in the direction perpendicular to the longitudinal
direction of the strip-shaped film and put along the film face, and
a strip-shaped conductive nonmagnetic film is formed zigzag on the
above-mentioned soft magnetic film with an electrical insulator
disposed therebetween, wherein the length of the part parallel to
the easy axis of magnetization of the film in the plane of the
above-mentioned soft magnetic film is made longer than the length
of the part orthogonal to the above-mentioned easy axis of
magnetization. The magnetic sensor further comprises a high
frequency power source for causing a high frequency current to flow
through the above-mentioned conductive nonmagnetic film, and a
detection circuit for detecting the above-mentioned external
magnetic field on the basis of the impedance change due to the
external magnetic field in the above-mentioned conductive
nonmagnetic film through which the above-mentioned high frequency
current flows.
[0010] According to the magnetic sensor of the other aspect, by
forming the soft magnetic film into the strip-shape, in addition to
the above-mentioned action and effect, when the external magnetic
field is applied, demagnetization field produced in the soft
magnetic film can be reduced. As a result, even in the case that a
high frequency carrier signal of a relatively low frequency is
used, the impedance value and the impedance change of the
conductive nonmagnetic film are large, and a magnetic sensor having
a high detection sensitivity is obtained.
[0011] The magnetic sensor of further aspect of the present
invention comprises a soft magnetic film formed on a principal
plane of a nonmagnetic substrate and having an easy axis of
magnetization in a predetermined direction conforming to the film
face, and a strip-shaped conductive nonmagnetic film formed zigzag
on the above-mentioned soft magnetic film with an intervenient
electrical insulation film, wherein the length of a portion
parallel to the easy axis of magnetization of the film in the plane
of the above-mentioned soft magnetic film is made longer than the
length of the portion orthogonal to the above-mentioned easy axis
of magnetization. The magnetic sensor further has a conductive film
for giving a direct current bias magnetic field to the
above-mentioned soft magnetic film by causing a direct current to
flow, which is formed on the above-mentioned conductive nonmagnetic
film with an intervenient insulative protection film. The magnetic
sensor further has a high frequency power source for causing a high
frequency current to flow through the above-mentioned conductive
nonmagnetic film, and a detection circuit for detecting the
above-mentioned external magnetic field on the basis of the
impedance change due to the external magnetic field in the
above-mentioned conductive nonmagnetic film through which the
above-mentioned high frequency current flows.
[0012] According to the magnetic sensor of the further aspect, in
addition to the above-mentioned actions and effects, the soft
magnetic film, the conductive nonmagnetic film and the conductive
film for giving the direct current bias magnetic field to the soft
magnetic film are held by a nonmagnetic substrate. The magnetic
sensor includes an effect which can detect the external magnetic
field with a high sensitivity by causing a direct current to flow
through the conductive film for applying a direct current bias
magnetic field.
[0013] A magnetic sensor of a further aspect of the present
invention comprises a strip-shaped first soft magnetic film formed
on a principal plane of a nonmagnetic substrate and having an easy
axis of magnetization in the direction perpendicular to the
longitudinal direction of the strip-shaped film and conforming to a
film face, and a strip-shaped conductive nonmagnetic film formed
zigzag on the above-mentioned soft magnetic film with an
intervenient first insulation film, wherein the length of a portion
parallel to the easy axis of magnetization of the film in the plane
of the above-mentioned soft magnetic film is made longer than the
length of a portion orthogonal to the above-mentioned easy axis of
magnetization. The magnetic sensor further comprises a second soft
magnetic film formed on the above-mentioned conductive nonmagnetic
film with an intervenient second insulation film, and having an
easy axis of magnetization in the direction perpendicular to the
longitudinal direction of the strip shape and conforming to the
film face, and a conductive film for giving a direct current bias
magnetic field to the above-mentioned soft magnetic film by causing
a direct current to flow, formed on the above-mentioned second soft
magnetic film with an intervenient insulation protection film. The
magnetic sensor further comprises a high frequency power source for
causing a high frequency current to flow through the
above-mentioned conductive nonmagnetic film, and a detection
circuit for detecting the above-mentioned external magnetic field
on the basis of the impedance change due to the external magnetic
field in the above-mentioned conductive nonmagnetic film through
which the above-mentioned high frequency current flows.
[0014] According to the magnetic sensor of the above-mentioned
further aspect, in addition to the above-mentioned respective
actions and effects, the following action and effect are included.
Since the strip-shaped conductive nonmagnetic film is interposed
between the first and the second soft magnetic films, an overall
thickness of the soft magnetic film substantially doubles.
Consequently, although demagnetization field increases when an
external magnetic field is applied to the magnetic sensor, the
absolute value of the impedance of the conductive nonmagnetic film
doubles. Since a detection output level of the detection circuit is
proportional to the value of the impedance, the level of the
detection output becomes high and the SN ratio of the detection
output becomes high.
[0015] The magnetic sensor of other aspect of the present invention
is characterized by comprising of at least one soft magnetic film
having a closed magnetic path formed by a soft magnetic film, a
conductive film for causing a direct current to flow, provided so
as to penetrate through the closed magnetic path of the
above-mentioned soft magnetic film, and a conductive nonmagnetic
film for causing a high frequency current to flow, provided so as
to penetrate through the closed magnetic path of the
above-mentioned soft magnetic film with keeping insulation to the
above-mentioned conductive film.
[0016] According to the present invention, since the conductive
film through which the direct current flows penetrates the closed
magnetic path, a large direct current bias magnetic field is
obtainable with a small direct current.
[0017] A fabrication method of the magnetic sensor in the present
invention comprises the step of forming at least one strip-shaped
first soft magnetic film being made to a lower soft magnetic film
on an upper face of a nonmagnetic substrate, the step of forming a
first conductive film on the above-mentioned first soft magnetic
film with an intervenient first insulation film, and a conductive
first connection part and a second connection part, the step of
forming a conductive nonmagnetic film on the above-mentioned first
conductive film with an intervenient second insulation film, the
step of forming a third insulation film on the above-mentioned
conductive nonmagnetic film, the step of removing the
above-mentioned first, second and third insulation films on the
above-mentioned first soft magnetic film so as to leave the
above-mentioned first, second and third insulation films in the
vicinity including the above-mentioned first conductive film and
the conductive nonmagnetic film, the step of forming a closed
magnetic path by providing a second soft magnetic film on the
above-mentioned first soft magnetic film and the above-mentioned
left first, second and third insulation films, the step of forming
a fourth insulation film on entire face including the
above-mentioned second soft magnetic film, the step of exposing the
above-mentioned first and second connection parts by removing the
second, the third and the fourth insulation films placed on the
above-mentioned first and second connection parts and forming
through holes, the step of forming connection lines of electric
conductors which are electrically connected to the above-mentioned
first and second connection parts at both ends, respectively, on
the above-mentioned fourth insulation film 94, and carrying out
connections with the first conductive film passing through adjacent
other closed magnetic path.
BRIEF DESCRIPTION OF DRAWINGS
[0018] FIG. 1 is a plane view of a magnetic sensor of a first
embodiment of the present invention.
[0019] FIG. 2 is a plane view showing a state in which a conductive
film 6 is removed from the magnetic sensor in FIG. 1.
[0020] Part (a) of FIG. 3 is a cross-sectional view taken along the
line III-III in FIG. 1.
[0021] Part (b) of FIG. 3 is an enlarged fragmentary view of a
right end portion of part (a) of FIG. 3.
[0022] FIG. 4 is a graph showing a relation of an external
magnetism Hex and an impedance Z of the magnetic sensor of the
first embodiment in the present invention.
[0023] FIG. 5 is a plane view showing the shape of a soft magnetic
film of the magnetic sensor of the first embodiment in the present
invention.
[0024] FIG. 6 is a graph showing a relation of the external
magnetism Hex and a magnetic flux density B in which a ratio L/W is
made to a parameter in the magnetic sensor of the first embodiment
in the present invention.
[0025] FIG. 7 is a graph showing a relation of the external
magnetism and the magnetic flux density B in which the thickness t
of the soft magnetic film is made to a parameter in the magnetic
sensor of the first embodiment in the present invention.
[0026] FIG. 8 is a plane view of the magnetic sensor of a second
embodiment in the present invention.
[0027] FIG. 9 is plane view showing a state in which the conductive
film 6 is removed from the magnetic sensor in FIG. 8.
[0028] FIG. 10 is a plane view of the magnetic sensor of other
example of the second embodiment in the present invention.
[0029] Part (a) of FIG. 11 is a cross-sectional view taken along
the line XI-XI in FIG. 10.
[0030] Part (b) of FIG. 11 is an enlarged fragmentary view of the
right end portion of part (a) of FIG. 11.
[0031] FIG. 12 is a graph showing a relation of the external
magnetism Hex and the impedance Z in the magnetic sensor of the
second embodiment in the present invention.
[0032] FIG. 13 is a plane view of the magnetic sensor of a third
embodiment in the present invention.
[0033] Part (a) of FIG. 14 is a cross-sectional view taken along
the line XIV-XIV in FIG. 13.
[0034] Part (b) of FIG. 14 is an enlarged fragmentary view of the
right end portion of Part (a) of FIG. 14.
[0035] Part (a) of FIG. 15 is a cross-sectional view of the
magnetic sensor of the third embodiment in the present
invention.
[0036] Part (b) of FIG. 15 is an enlarged fragmentary view of the
right end portion of Part (a) of FIG. 15.
[0037] Part (a) of FIG. 16 is a cross-sectional view of the
magnetic sensor of a fourth embodiment in the present
invention.
[0038] Part (b) of FIG. 16 is an enlarged fragmentary view of the
right end portion of part (a) of FIG. 16.
[0039] FIG. 17 is a plane view of the magnetic sensor of a fifth
embodiment in the present invention.
[0040] FIG. 18 is a plane view showing a state in which the
conductive film 6 is removed from the magnetic sensor in FIG.
17.
[0041] Part (a) of FIG. 19 is a cross-sectional view taken along
the line XIX-XIX in FIG. 18.
[0042] Part (b) of FIG. 19 is an enlarged fragmentary view of the
right end portion of Part (a) of FIG. 19.
[0043] Part (a) of FIG. 20 is a cross-sectional view of the
magnetic sensor of the fifth embodiment in the present
invention.
[0044] Part (b) of FIG. 20 is an enlarged fragmentary view of the
right end portion of part (a) of FIG. 20.
[0045] FIG. 21 is a plane view of a magnetic sensor of a sixth
embodiment in the present invention.
[0046] Part (a) of FIG. 22 is a cross-sectional view taken along
the line XXII-XXII in FIG. 21.
[0047] Part (b) of FIG. 22 is an enlarged fragmentary view of the
right end portion of Part (a) of FIG. 22.
[0048] Part (a) of FIG. 23 is a cross-sectional view of the
magnetic sensor in other example of the sixth embodiment in the
present invention.
[0049] Part (b) of FIG. 23 is an enlarged fragmentary view of the
right end portion of part (a) of FIG. 23.
[0050] FIG. 24,is a plane view of the magnetic sensor of a seventh
embodiment in the present invention.
[0051] Part (a) of FIG. 25 is a cross-sectional view of the
magnetic sensor of the seventh embodiment in the present
invention.
[0052] Part (b) of FIG. 25 is an enlarged fragmentary view of the
right end portion of part (a) of FIG. 25.
[0053] FIG. 26 is a plane view of the magnetic sensor of an eighth
embodiment in the present invention.
[0054] FIG. 27 is a plane view of the soft magnetic film in the
magnetic sensor of the eighth embodiment in the present
invention.
[0055] FIG. 28 is a plane view for describing a problem of the soft
magnetic films of the above-mentioned second embodiment to seventh
embodiment.
[0056] FIG. 29 is a graph showing a relation of the external
magnetic field and the magnetic flux density of the soft magnetic
film in FIG. 28.
[0057] FIG. 30 is a graph showing a relation of the external
magnetic field and the impedance in the soft magnetic film in FIG.
28.
[0058] FIG. 31 is a plane view showing a magnetic flux in the soft
magnetic film of the present embodiment.
[0059] FIG. 32 is a graph showing the change of the magnetic flux
density of the soft magnetic film in the present embodiment when a
dimension S is changed.
[0060] FIG. 33 is a perspective view of the magnetic sensor of a
ninth embodiment in the present invention.
[0061] FIG. 34 is a plane view of the magnetic sensor of the ninth
embodiment in the present invention.
[0062] Parts (a) to (d) of FIG. 35 are cross-sectional views taken
along the line XXXV-XXXV in the longitudinal direction of the soft
magnetic film, showing a fabricating process of the magnetic sensor
of the ninth embodiment in the present invention.
[0063] Parts (a) to (d) of FIG. 36 are cross-sectional views taken
along the line XXXVI-XXXVI in the perpendicular direction to the
longitudinal direction of the soft magnetic film, showing a
fabricating process of the magnetic sensor of the ninth embodiment
in the present invention.
[0064] FIG. 37 is a partial perspective view of the magnetic sensor
of a tenth embodiment in the present invention.
[0065] FIG. 38 is a plane view of the magnetic sensor of the tenth
embodiment in the present invention.
[0066] Parts (a) to (d) of FIG. 39 are cross-sectional views taken
along the line XXXIX-XXXIX in the longitudinal direction of the
soft magnetic film, showing a fabricating process of the magnetic
sensor of the tenth embodiment in the present invention.
[0067] Parts (a) to (d) of FIG. 40 are cross-sectional views taken
along the line XXXX-XXXX in the perpendicular direction to the
longitudinal direction of the soft magnetic film, showing a
fabricating process of the magnetic sensor of the tenth embodiment
in the present invention.
[0068] Parts (a) to (d) of FIG. 41 are cross-sectional views for
describing the magnitude of a direct current bias magnetic field
which depends on the positional relation of the soft magnetic film
and a conductive nonmagnetic film producing a direct current bias
magnetic field.
[0069] Part (a) of FIG. 42 is the perspective view of the magnetic
sensing element utilizing a magnetic impedance effect in the prior
art.
[0070] Part (b) of FIG. 42 is the partially enlarged view of the
soft magnetic core 105, 106 of the magnetic sensing element in the
prior art.
[0071] FIG. 43 is the graph showing a characteristic of the
magnetic sensing element in the prior art.
BEST MODE FOR CARRYING OUT THE INVENTION
[0072] Hereinafter, preferred embodiments of the magnetic sensor in
the present invention are described with reference to FIG. 1 to
FIG. 41.
FIRST EMBODIMENT
[0073] Description is made as to a magnetic sensor 9 of a first
embodiment in the present invention with reference to FIG. 1 to
FIG. 7.
[0074] FIG. 1 is a plane view of the magnetic sensor 9 of the first
embodiment in the present invention. FIG. 2 shows a plane view in a
situation in which a conductive film 6 of copper (Cu) for applying
a direct current bias magnetic field in FIG. 1 is removed in order
to facilitate the understanding of inside structure. In order to
avoid complication of the figures and to facilitate understanding,
in all plane views including FIG. 1 and FIG. 2, depressions and
projections existing on the surfaces are omitted from illustration.
Part (a) of FIG. 3 is a cross-sectional view taken along the line
III-III in FIG. 1, and part (b) of FIG. 3 is an enlarged
fragmentary cross-sectional view of part (a) of FIG. 3. In
cross-sectional views, in order to avoid complication of figures,
cross-sections are not hatched.
[0075] In FIG. 1, FIG. 2, part (a) of FIG. 3 and part (b) of FIG.
3, a soft magnetic film 4 of Fe--Ta--N of 1 .mu.m thick is formed
at a central region on a nonmagnetic substrate 1. For example,
ceramic including NiO of an oxide of Nickel, TiO.sub.2 of an oxide
of Titan and MgO of an oxide of Magnesium (hereinafter is referred
to as Ni--Ti--Mg) is suitable for the nonmagnetic substrate 1. The
soft magnetic film 4 is formed so as to have the easy axis of
magnetization in the direction of arrow 80 which is along with the
film face. An insulation film 5 of SiO.sub.2 of 0.1 .mu.m thick is
formed on the soft magnetic film 4. A conductive nonmagnetic film 7
of meander shape (zigzag shape) of 1 .mu.m thick Cu having
electrode terminals 3 and 3A at either end as shown in FIG. 2 is
formed on the insulation film 5. The lengths of conductive
nonmagnetic films 7A and 7B which are parts parallel to the
direction of the arrow 80 in the conductive nonmagnetic film 7 of
meander type are made longer than the lengths of conductive
nonmagnetic films 7C and 7D which are parts perpendicular to the
direction of the arrow 80. In FIG. 2, the lengths of the conductive
nonmagnetic films 7A and 7B are made longer than the length of the
soft magnetic film 4 in the direction of the arrow 80 so that the
conductive nonmagnetic films 7C and 7D protrude outward from the
soft magnetic film 4. In part (a) of FIG. 3, the conductive
nonmagnetic film through which a current flows from front side to
back side of the paper face is designated as 7A, and the conductive
nonmagnetic film through which the current flows in the opposite
direction thereof is designated as 7B.
[0076] Subsequently, a protection film 8 of SiO.sub.2 of 10 .mu.m
thick is formed on the insulation film 5 including the conductive
nonmagnetic film 7 as shown in part (a) of FIG. 3. A conductive
film 6 having electrodes 2A and 2B at either end part as shown in
FIG. 1 is formed on the protection film 8. The size of the
conductive film 6 is about the same as the size of the soft
magnetic film 4. A film of a stable metal such as gold (Au) of
about 4 .mu.m thick is formed on the electrodes 2A and 2B of the
conductive film 6 and connection parts of the electrodes 2A, 2B and
the conductive film 6 so as to provide a large current capacity.
Incidentally, the above-mentioned electrodes 3 and 3A may be made
thick in a similar manner.
[0077] The negative (output) end and the positive end of the direct
current source 10 are connected to the electrodes 2A and 2B of the
conductive film 6, respectively, and a direct current is caused to
flow through the conductive film 6. A constant current high
frequency source 11 including a high frequency oscillator of 10
MHz-20 MHz of frequency is connected to the electrode terminals 3
and 3A of the conductive nonmagnetic film 7 through a resistor 12,
and a high frequency current of a constant current is caused to
flow. Furthermore, respective input terminals of a high frequency
amplifier 13 including an AM detector are connected to the
electrode terminals 3 and 3A. As shown in part (a) of FIG. 3 and
part (b) of FIG. 3, the direct current flows through the conductive
film 6 perpendicularly to the paper face from its front side to the
back side. In the right and left parts of the figure, the widths of
the conductive film 6 are made approximately equal to the width of
the soft magnetic film 4, and therefore, a direct current magnetic
field shown by arrow 14 indicated by dotted line is produced around
the conductive film 6. A magnetic flux passes from the right end to
the left end of the soft magnetic film 4 due to the direct current
magnetic field 14 as shown in expanded scale in part (b) of FIG. 3,
and affects as a direct current bias magnetic field (Hbias) to the
soft magnetic film 4.
[0078] A high frequency carrier current of a constant current
supplied from the high frequency power source 11 flows through the
conductive nonmagnetic film 7 of meander type. Part (b) of FIG. 3
shows an instant at which a current flows through the cross section
7A of the conductive nonmagnetic film 7 in the direction
perpendicular to the paper face from front side to back side, and
the current flows through the cross section 7B of the conductive
nonmagnetic film 7 in the opposite direction thereof. Since this
current is an alternating current at a high frequency of the
above-mentioned 10 MHz-20 MHz, this current produces an alternating
magnetic field alternately inverting the direction every half cycle
of the alternating current in crock wise and counter crock wise as
shown by respective arrows 15. The impedance of the conductive
nonmagnetic film 7 with respect to the high frequency current is
determined according to the alternating current magnetic field and
the direct current bias magnetic field shown by the arrow 14.
[0079] As shown in FIG. 1 and FIG. 2, an external magnetic field
Hex (hereinafter is referred to as external magnetic field Hex 16)
which is in the direction shown by an arrow 16 and is an object to
be measured is applied to the soft magnetic film 4 of the magnetic
sensor 9 in the longitudinal direction. A permeability of the soft
magnetic film 4 to which the direct current bias magnetic field is
applied varies corresponding to the magnitude of this external
magnetic field Hex 16. As a result, the impedance of the conductive
nonmagnetic film 7 varies. Consequently, a high frequency voltage
which is the product of the high frequency current and the
impedance is generated across the electrode terminals 3 and 3A. The
high frequency voltage is a signal of which the high frequency
carrier signal is amplitude-modulated corresponding to the
magnitude of the external magnetic field Hex 16. Detection signal
of the external magnetic field Hex 16 is obtained by AM detection
and amplification of the amplitude-modulated signal with a high
frequency amplifier 13. The magnetic fields produced by the high
frequency current flowing through the conductive nonmagnetic films
7A and 7B spread partly into other regions, but the major part is
concentrated locally to the soft magnetic film 4 at respective
lower regions as shown by the arrow 15 in part (b) of FIG. 3.
Therefore, a high frequency magnetic field which is superimposed on
the direct current bias magnetic field is produced in the regions
of the soft magnetic film 4 opposing to the conductive nonmagnetic
films 7A and 7B. There are a plurality of opposing regions of the
soft magnetic film 4 and the conductive nonmagnetic film 7 (8
regions in FIG. 2), and therefore, the impedance due to mutual
inductance between mutually opposing regions increases with the
increase of number (n) of the opposing regions. The impedance can
be adjusted by changing film width D and interval T between the
neighboring conductive nonmagnetic films 7B and 7E.
[0080] In FIG. 2, when impedance arising in the conductive
nonmagnetic film 7 at one opposing region 70 of the soft magnetic
film 4 and the conductive nonmagnetic film 7 is provided as Z0,
then in the case that the number (n) of the opposing regions is two
as shown in part (b) of FIG. 3, when the direct current bias
magnetic field is Hbias as shown by FIG. 4, the impedance value is
2.times.Z0. FIG. 5 is a plane view showing a situation in which the
rectangular-shaped soft magnetic film 4 of Fe--Ta--N of a width W
is placed in the external magnetic field Hex 16 to be measured. As
a result of investigation of demagnetization field produced in the
soft magnetic film 4 of FIG. 5, it is found that the magnitude of
the demagnetization field is changed depending on the shape of the
soft magnetic film 4. FIG. 6 is a graph of measurement result of a
relation between a magnetic flux density B (axis of ordinates) on a
center line c-d of the soft magnetic film 4 and an external
magnetic field Hex (axis of abscissas) by changing a dimensional
ratio L/W of the soft magnetic film 4 shown in FIG. 5. A film of
Fe--Ta--N which is 1 .mu.m in thickness t and has the easy axis of
magnetization in the direction of width W is used for the soft
magnetic film 4. When the direction of the external magnetic field
Hex is in coincident with the direction of the hard axis of
magnetization perpendicular to the easy axis of magnetization of
the soft magnetic film 4, rotation of magnetization is smoothly
carried out and a high permeability is achieved. Therefore, as
shown in FIG. 6, the larger the value of the dimensional ratio L/W
becomes, the higher the magnetic flux density B becomes even in a
weak external magnetic field Hex 16. This is considered to be the
influence of demagnetization field which is produced depending on
the shape of the soft magnetic film 4 as is well known in the
electromagnetics. FIG. 7 is a graph of measurement of the relation
of a magnetic flux density B on the centerline c-d of the soft
magnetic film and to the external magnetic field Hex to be measured
by setting the dimensional ratio L/W to 1 and changing the
thickness t of the soft magnetic film 4 which is a parameter. In
the case of measuring geomagnetism about 0.3 Oe or below (24 A/m in
SI unit system) in the magnitude as the external magnetic field
Hex, it is preferable that the thickness of the soft magnetic film
4 is 1 .mu.m and below, and the dimensional ration L/W is 5 or more
when influence of the demagnetization field is considered. The
magnitude of the demagnetization field become small with reduced
thickness of the soft magnetic film 4 and with increased
dimensional ratio L/w.
[0081] As shown in FIG. 7, the thinner the soft magnetic film 4 is,
the higher the magnetic flux density B achieved is, even in a weak
external magnetic field. According to FIG. 7, in the case that the
value of the dimensional ratio L/W is set to 1, the thickness of
the soft magnetic film 4 is preferably 0.2 .mu.m and below.
However, in the case that the thickness t of the soft magnetic film
4 is excessively thin, the impedance of the conductive nonmagnetic
film 7 becomes small at a high frequency. Accordingly, as a result
of conducting various experiments by the inventors, the
above-mentioned dimensional ratio L/W is set to 10 or more, and the
thickness t of the soft magnetic film 4 is set to 3 .mu.m and
below. By setting in this manner, it is found that the geomagnetism
on the order of 0.3 Oe (24 A/m) can be detected with a high
sensitivity. Consequently, a magnetic sensor having a high
sensitivity is obtainable by setting the film thickness of the soft
magnetic film 4 to 3 .mu.m and below in the magnetic impedance
element using a high frequency carrier signal of a relatively low
frequency on the order of 10 MHz to 20 MHz. Since a low frequency
carrier signal can be used, error due to the length of lead wires
to the sensor or the change of shape thereof is reduced.
SECOND EMBODIMENT
[0082] A magnetic sensor of the second embodiment in the present
invention is described with reference to FIG. 8 to FIG. 12.
[0083] In the case that the frequency of the high frequency carrier
signal applied to the magnetic sensor utilizing the
magnetoimpedance effect is relatively low, in which carrier
frequency is from 10 MHz to 20 MHz, the impedance of the conductive
nonmagnetic film 7 of the above-mentioned magnetic sensor 9 in FIG.
1 is given principally by the product of the above-mentioned
frequency and inductance of the conductive nonmagnetic film 7.
Accordingly, in the present embodiment, the demagnetization field
of the soft magnetic film 4 of the above-mentioned first embodiment
is reduced, thereby to increase the inductance of the conductive
nonmagnetic film 7, such that the impedance changes become large
even with a weak magnetic field such as geomagnetism.
[0084] FIG. 8 is a plan view of a magnetic sensor of the second
embodiment. Referring to the figure, a plurality of narrow
strip-shaped soft magnetic films 44 of Fe--Ta--N, of which the
dimensional ratio L/W is selected such a large value of 10 or more
in order to reduce the demagnetization field, which has been
explained in the first embodiment, are formed on a nonmagnetic
substrate 1 of Ni--Ti--Mg. The plural strip-shaped soft magnetic
films 44 which are parallel arranged correspond to the soft
magnetic film 4 in the first embodiment. The soft magnetic films 44
have the easy axis of magnetization in a width direction (arrow 80)
which is along with the film face. As shown in FIG. 9, a
meander-shaped conductive nonmagnetic film 7 orthogonal to the soft
magnetic films 44 is formed on the soft magnetic films 44 with an
insulation film 5 therebetween. Referring to FIG. 9, the soft
magnetic films 44 are placed under the insulation film 5, and the
conductive nonmagnetic film 7 is placed on the insulation film 5.
As shown in FIG. 8, a conductive film 6 of the same material and
shape as that in FIG. 1 is formed on the conductive nonmagnetic
film 7 and the insulation film 5, and thereby the magnetic sensor
9A is configured. FIG. 9 shows a plan view in the state with the
conductive film 6 of FIG. 8 removed to facilitate an understanding
of the configuration of the conductive nonmagnetic film 7. A
cross-sectional view taken along the line III-III in FIG. 8 is
substantially the same as part (a) of FIG. 3.
[0085] According to the magnetic sensor 9A of the present
embodiment, the demagnetization field generated in the soft
magnetic films 44 considerably decreases in comparison with that in
the soft magnetic film 4 in FIG. 1. The number of opposing parts
70A, at which each of the soft magnetic films 44 faces the
conductive nonmagnetic film 7, is increased by increasing the
number of the soft magnetic films 44. As a result, there is the
characteristic in that the impedance value becomes large in
comparison with the configuration of FIG. 1 and a large impedance
change is obtainable.
[0086] FIG. 10 is a plan view of a magnetic sensor 9B of a
configuration in other example of the second embodiment. In this
configuration, as shown by part (a) of FIG. 11, and part (b) of
FIG. 11 which is an enlarged cross-sectional view of part (a) of
FIG. 11, first, the conductive film 6 for applying a direct current
bias magnetic field is formed on the nonmagnetic substrate 1 of
Ni--Ti--Mg. The soft magnetic films 44 are formed on the conductive
film 6 with a SiO.sub.2 film 21 therebetween. The insulation film 5
is formed on the soft magnetic films 44 and the SiO.sub.2 film 21.
The meander-shaped conductive nonmagnetic film 7 is formed on the
insulation-film 5. An insulation film 8 of SiO.sub.2 of about 1
.mu.m thick is formed on the insulation film 5 including the
conductive nonmagnetic film 7 as a protection film. In the
configuration of part (a) of FIG. 11, the forming of the conductive
film 6 is easy in fabrication, and furthermore, the surface of the
conductive film 6 is flat because the conductive film 6 is formed
on a flat surface of the nonmagnetic substrate 1, and thus a
sufficient insulation is maintained even if the insulation film 21
formed on the flat surface is made considerably thin. Consequently,
the distance between the conductive film 6 and the soft magnetic
films 44 is made small, and strong bias magnetic field generated by
the conductive film 6 as shown by arrow 14 indicated by dotted line
is applied to the soft magnetic films 44. As a result, a direct
current flowing-through the conductive film 6 can be reduced
compared with that of the configuration of FIG. 1. In other words,
there is a feature that a power consumption of the direct current
bias power source 10 can be reduced.
[0087] FIG. 12 is a graph showing a relation of the impedance Z of
the conductive nonmagnetic film 7 and an external magnetic field
Hex using the width W1 (FIG. 10) of the soft magnetic films 44 as
parameter. Curves C1, C2 and C3 are graphs in the case that the
width W1 is 10 .mu.m, 100 .mu.m and 400 .mu.m, respectively. The
impedance Z is shown by normalizing with an impedance value of the
case that the external magnetic field Hex to be measured is zero.
The thickness of the soft magnetic films 44 is 3 .mu.m, and the
length L thereof is 1 mm. The measurement is carried out by placing
the magnetic sensor 9B in the external magnetic field. As a result,
as shown in FIG. 12, it is found that the smaller the width W1 of
the soft magnetic films 44 is, the larger an impedance change is
even in a weak external magnetic field Hex to be measured. In the
measurement of geomagnetism which is weak in the magnitude of the
magnetic field, those of the curves C1 and C2 (width W1 is 10 .mu.m
or 100 .mu.m) are adequate. That of the curve C3 is inferior in
sensitivity, and was not suitable to detect the geomagnetism. By
the above-mentioned result, it was found that a desirable width W1
of the soft magnetic films 44 is 100 .mu.m and below, the
dimensional ratio L/W1 is 10 or more. The film thickness and the
film width of the conductive nonmagnetic film 7 of meander type are
set to 1.0 .mu.m and 10 .mu.m, respectively. As a concrete example
of the magnetic sensor in the second embodiment, it is desirable
that a length K and a width T of the conductive nonmagnetic film 7
are 1 mm and 100 .mu.m, respectively, and the width W1 of the soft
magnetic films 44 is 40 .mu.m, the length L thereof is 1 mm.
[0088] In the present embodiment, a plurality of soft magnetic
films 44 of which the dimensional ratio L/W1 is 10 or more and the
film thickness is 3 .mu.m and below are opposed to the conductive
nonmagnetic film 7 of meander type. Consequently, even in the case
of the use of a relatively low carrier frequency of 10 MHz-20 MHz,
the impedance change of the conductive nonmagnetic film 7 due to
the external magnetic field can be greatly increased. As mentioned
above, since a carrier signal of a low frequency can be used,
errors due to the change of the length and the shape of electric
wires to the sensor can be reduced.
THIRD EMBODIMENT
[0089] A magnetic sensor 9C of the third embodiment in the present
invention is described with reference to FIG. 13 to FIG. 15.
[0090] FIG. 13 is a plan view of the magnetic sensor 9C of the
third embodiment in the present invention, and part (a) and part
(b) of FIG. 14 are cross-sectional views taken along the line
XIV-XIV in FIG. 13. In part (a) of FIG. 14 and part (b) of FIG. 14
of an enlarged fragmentary cross-sectional view, a film 18
including Cobalt (Co) and Platinum (Pt) (hereinafter is referred to
as Co--Pt film) is formed on a nonmagnetic substrate 1 of
Ni--Ti--Mg. The film 18 is magnetized so as to form the N and S
poles in the right and left directions of the figure. Consequently,
the Co--Pt film 18 becomes a permanent magnet film 18. Strip-shaped
soft magnetic films 44 similar to those of the above-mentioned
second embodiment are formed in approximately the same region as
the permanent magnet film 18 on the permanent magnet film 18.
Subsequently, an insulation film 5 is formed so as to cover the
soft magnetic films 44 and the permanent magnet film 18. The
conductive nonmagnetic film 7 of meander type is formed on the
insulation film 5. An insulation film 8 of about 1 .mu.m thick
SiO.sub.2 is formed on the conductive nonmagnetic film 7 as a film
for protection, thereby the magnetic sensor 9C is configured.
[0091] In the magnetic sensor 9C of the present embodiment, as
shown in part (b) of FIG. 14, a magnetic flux shown by an arrow 22
indicated by dotted line caused by the permanent magnet film 18
passes through the soft magnetic films 44, and a direct current
bias magnetic field is applied to the soft magnetic films 44.
Therefore, in the present embodiment, a direct current power source
for generating the direct current bias magnetic field is Knot
required. When a high frequency current is passed through the
conductive nonmagnetic film 7, an alternating current magnetic
field is generated as shown by an arrow 15 indicated by dotted line
in part (b) of FIG. 14.
[0092] Part (a) of FIG. 15 and part (b) of FIG. 15 of a partially
enlarged figure are cross-sectional views showing other example of
magnetic sensor in the present embodiment. In the figure, the
strip-shaped soft magnetic films 44 are formed on the nonmagnetic
substrate 1 of Ni--Ti--Mg. Subsequently, the insulation film 5 is
formed on the nonmagnetic substrate 1 including the soft magnetic
films 44. The conductive nonmagnetic film 7 of meander type is
formed on the insulation film 5, and further, a Co--Pt film 19 is
formed on the conductive nonmagnetic film 7. The Co--Pt film 19 is
magnetized in the longitudinal direction of the soft magnetic films
44 (in the right and left direction in part (b) of FIG. 15) as
shown in an enlarged fragmentary sectional view of part (b) of FIG.
15, thereby to make the Co--Pt permanent magnet film 19 having the
magnet poles of N and S in the width direction of Co--Pt film 19,
namely in the longitudinal direction of the soft magnetic films 44.
The direct current bias magnetic field is applied to the soft
magnetic films 44 facing to the conductive nonmagnetic film 7 by
the magnetic flux 20 from the permanent magnet film 19. In general,
a soft magnetic body is decreased in permeability by being applied
a direct current magnetic field. In the present embodiment, the
direct current bias magnetic field is applied to only the parts of
the soft magnetic films 44 facing to the permanent magnet film 19,
and is not applied to other major parts. Therefore, the parts of
the soft magnetic films 44 in which the permeability lowers are
limited, and the soft magnetic films 44 are prevented from the
lowering of permeability in all areas. In other words, the major
parts of the soft magnetic films 44 maintain original permeability.
Consequently, the density of magnetic-flux due to the external
magnetic field Hex 16 and passing through the soft magnetic films
44 does not lower much, and an action which the magnetic flux due
to the external magnetic field gives to the impedance change of the
conductive nonmagnetic film 7 can be utilized to its maximum.
Thereby a magnetic sensor having a high sensitivity is
obtainable.
FOURTH EMBODIMENT
[0093] A magnetic sensor 9D of the fourth embodiment in the present
invention is described with reference to FIG. 16.
[0094] Part (a) of FIG. 16 and part (b) of FIG. 16 are
cross-sectional views of the magnetic sensor 9D of the fourth
embodiment in the present invention. The plan view of the magnetic
sensor 9D is similar to FIG. 8. FIG. 16 is a cross-sectional view
showing the same cross section as the III-III cross section in FIG.
8. In the magnetic sensor 9D of the present embodiment, a
conductive film 6 is formed on the protection film 8 of the
magnetic sensor 9C shown in part (a) of FIG. 14, and other
configuration is the same as the magnetic sensor 9C. In the
magnetic sensor 9C, the direct current bias magnetic field is given
by the magnetic field of the permanent magnet film 18, but it is
difficult to apply an optimum direct current bias magnetic field
because of variations in magnetic characteristics of the soft
magnetic films 44 or variations of the magnetic force of the
permanent, magnet film 18. In the magnetic sensor 9D of part (a) of
FIG. 16, a weak direct current bias magnetic field shown by arrow
14 indicated by dotted line is generated by passing minute
direct-current through the conductive film 6. The direct current
bias magnetic field produced by the direct current is superimposed
on the main direct current bias magnetic field produced by the
permanent magnet film 18 shown by arrow 22 indicated by dotted line
in part (b) of FIG. 16, thereby the magnitude of the direct current
bias magnetic field by the permanent magnet film 18 can be finely
adjusted. Since the direct current bias magnetic field can be
increased or decreased by adjusting the current of the conductive
film 6, an, optimum direct current bias magnetic field is easily
produced. Consequently, the magnetic sensor having a high
sensitivity is obtainable.
FIFTH EMBODIMENT
[0095] A magnetic sensor 9E of the fifth embodiment of the present
invention is described with reference to FIG. 17 to FIG. 20. FIG.
17 is a plan view of the magnetic sensor of the present embodiment,
and FIG. 18 is a plan view in which the conductive film 6 in FIG.
17 is removed and the configurations of the soft magnetic films 44
and the conductive nonmagnetic film 7 are made easier to
understand. Part (a) of FIG. 19 is a XIX-XIX cross-sectional view
of FIG. 17, and part (b) of FIG. 19 is an enlarged fragmentary
cross-sectional view of part (a) of FIG. 19. Referring to FIG. 18
and part (a) of FIG. 19, a plurality of strip-shaped first soft
magnetic films 44 are formed in a central region of the nonmagnetic
substrate 1 of Ni--Ti--Mg, and the insulation film 5 is formed so
as to cover thereon. The conductive nonmagnetic film 7 of meander
type is formed on the insulation film 5, and an insulation film 24
of SiO.sub.2 is formed on an entire face of the insulation film 5
including the conductive nonmagnetic film 7. Subsequently, a second
soft magnetic film 23 of the same shape and the same material as
those of the soft magnetic films 44 is formed on the insulation
film 24 so as to be located directly above the each soft magnetic
film 44. Furthermore, a protection film 8 is formed on an entire
face of the insulation film 24 including the soft magnetic film 23,
and a conductive film 6 is formed on the protection film 8.
[0096] According to the configuration of the present embodiment,
since the conductive nonmagnetic film 7 is interposed between two
soft magnetic films 23 and 44, a total thickness of the soft
magnetic films becomes substantially twice. By this configuration,
the magnetic flux due to the high frequency current flowing through
the conductive nonmagnetic film 7 passes through the closed loop
including the soft magnetic films 23 and 44 as shown by arrow 15 in
part (b) of FIG. 19, therefore, the magnetic flux density becomes
high.
[0097] In the magneto-impedance element, an absolute value of the
magneto-impedance increases in proportional to the thickness of the
soft magnetic film. On the other hand, when the thickness of the
soft magnetic film increases, the sensitivity of the magnetic
sensor lowers because of increase of the demagnetization field due
to the external magnetic field. However, when the impedance is
large, the detected output level which is the product of the
impedance and the high frequency carrier current becomes large, and
an SN ratio of the detected output becomes high. The magnetic
sensor of the present embodiment is suitable for a use which is
desirable to obtain a high detected output, even if a detection
sensitivity is low.
[0098] In the magnetic sensor of the present embodiment, in order
to minimize the demagnetization field and maximize the sensitivity,
it is desirable that the respective film thicknesses of the soft
magnetic films 23 and 44 are 1.5 .mu.m and below, and a total
thickness is 3 .mu.m and below.
[0099] In part (a) of FIG. 19, when a direct current is passed
through the conductive film 6, a magnetic flux of the direct
current bias magnetic field shown by arrow 14 is generated. The
magnetic fluxes of the direct current bias magnetic field pass
through the soft magnetic films 23 and 44 as shown by respective
arrows 25 and 26 indicated by dotted lines shown in part (b) of
FIG. 19, and apply the direct current bias magnetic field.
[0100] Part (a) of FIG. 20 and part (b) of FIG. 20 are
cross-sectional views showing structure in the case that the
magnetic sensor of other example of the present embodiment is made
by using the photolithography method. By using the photolithography
method, the insulation films 5 and 24 in part (b) of FIG. 19 can be
formed only the circumference of the conductive nonmagnetic film 7
as the insulation films 5A and 24A in part (b) of FIG. 20. By this
structure, two soft magnetic films 23 and 44 contact with each
other between adjacent conductive nonmagnetic films 7.
Consequently, the magnetic flux of the high frequency magnetic
field shown by arrow 15 indicated by dotted line generated in the
circumference of the conductive nonmagnetic film 7 concentrates in
the vicinity of the conductive nonmagnetic film 7, and a mutual
action of which-the respective magnetic fields of the adjacent
conductive nonmagnetic films 7 affect with each other decreases. By
the decrease of the mutual action, the impedance value becomes
large. Furthermore, since the interval T of the meander type
conductive nonmagnetic film 7 can be reduced, the impedance value
can be further increased. Consequently, the impedance change of the
conductive nonmagnetic films 7 further increases when the external
magnetic field Hex 16 is applied, and the detection sensitivity of
the magnetic sensor becomes high.
SIXTH EMBODIMENT
[0101] A magnetic sensor 9F of the sixth embodiment in the present
invention is described with reference to FIG. 21 to FIG. 23.
[0102] FIG. 21 is a plan view of the magnetic sensor 9F of the
sixth embodiment in the present invention, and part (a) of FIG. 22
is a XXII-XXII cross-sectional view of FIG. 21. FIG. 21 shows a
state in which the protection film 8 of the most upper layer is
removed. Part (b) of FIG. 22 is an enlarged fragmentary
cross-sectional view of part (a) of FIG. 22. In FIG. 21 and part
(a) of FIG. 22, a plurality of strip-shaped first soft magnetic
films 44 are formed on the nonmagnetic substrate 1 of Ni--Ti--Mg. A
Co--Pt film 18 having width W4 smaller than a side to side width W3
of the soft magnetic films 44 in the, figure is formed on the
nonmagnetic substrate 1 including the soft magnetic films 44. The
conductive nonmagnetic film 7 of a meander type is formed on the
Co--Pt film 18 with an insulation film 5A therebetween. After
forming an insulation film 24A around the circumference of the
meander-type conductive nonmagnetic film 7, other second soft
magnetic films 23 of the same shape and the same material as the
soft magnetic films 44 are formed on the surface including the
insulation film 24A around the circumference of the conductive
nonmagnetic film 7 and the above-mentioned Co--Pt film 18 so as to
be located just above the soft magnetic films 44.
[0103] Furthermore, the protection film 8 is formed on the entire
surface including the soft magnetic films 23. The Co--Pt film 18 is
magnetized so that N and S poles are formed in the right and left
directions in the figure, and thereby the Co--Pt film 18 is made to
be the permanent magnet. The width W4 of the Co--Pt film 18 is made
smaller than the width W3 of the soft magnetic films 23 and 44,
thereby the soft magnetic films 23 and 44 come into contact with
each other at their both ends. Consequently, the magnetic flux
generated by the permanent magnet of Co--Pt film 18 passes through
the soft magnetic films 23 and 44 as shown by arrows 22 indicated
by dotted lines, and the direct current bias magnetic field is
applied to both the soft magnetic films 23 and 44.
[0104] Part (a) of FIG. 23 is a cross-sectional view showing the
same cross section as FIG. 22 showing other configuration example
of the present embodiment, and part (b) of FIG. 23 is an enlarged
fragmentary cross-sectional view of part (a) of FIG. 23.
[0105] In the configuration shown by part (a) of FIG. 23 and part
(b) of FIG. 23, a Co--Pt film 19 having width W6 which is slightly
wider than the width W5 of the conductive nonmagnetic film 7 is
opposed to the conductive nonmagnetic film 7 with the insulation
film 5A therebetween. The Co--Pt film 19 having such a shape can be
formed by using the photolithography method. The Co--Pt film 19 is
magnetized so as to form N and S poles in the right and left
directions in the figure, and thereby forming a permanent magnet.
As shown in part (b) of FIG. 23, the magnetic fluxes generated by
the Co--Pt film 19 of the permanent magnet pass through the soft
magnetic films 23 and 44 as shown by arrows 20 indicated by dotted
lines, and a local direct current bias magnetic field is applied to
the parts of both the soft magnetic films 23 and 44 in the vicinity
of the conductive nonmagnetic film 7. If the direct current bias
magnetic field is applied to the entire soft magnetic films 23 and
44, the permeabilities of the entire soft magnetic films 23 and 44
have tendencies to lower. According to the configuration shown in
FIG. 23, since the direct current bias magnetic field is applied to
the soft magnetic films 23 and 44 only in the vicinity of the
conductive nonmagnetic film 7, the decrease in the permeability of
the soft magnetic films 23 and 44 is limited at a local part and
the overall reduction is prevented. As a result, the impedance
change of the conductive nonmagnetic film 7 caused by the external
magnetic field increases, and a high detection sensitivity is
obtainable.
[0106] The magnetic field generated by the Co--Pt film 19 is
restricted within the magnetic circuit of a closed loop by the soft
magnetic films 23 and 44, and the magnetic flux leakage to the
outside is reduced. Therefore, magnetic influence which is given to
other components in the device provided with this magnetic sensor
can be limited to a minimum.
[0107] According to the present embodiment, since the direct
current magnetic bias is applied by the Co--Pt film 18 or 19 of
permanent magnet, there is no need to have a direct current power
source for applying the direct current magnetic bias by passing a
direct current through the conductive film 6 as the above-mentioned
first, second and fifth embodiments. From this point, power
consumption is lower in the magnetic sensor of the present
embodiment.
SEVENTH EMBODIMENT
[0108] A magnetic sensor 9G of the seventh embodiment of the
present invention is described with reference to FIG. 24 and FIG.
25.
[0109] FIG. 24 is a plan view of the magnetic sensor 9G of the
seventh embodiment in the present invention. Part (a) of FIG. 25 is
a XXV-XXV cross-sectional view of FIG. 24, and part (b) of FIG. 25
is an enlarged fragmentary cross-sectional view of part (a) of FIG.
25. In part (b) of FIG. 25, the conductive film 6 is formed on the
nonmagnetic substrate 1 of Ni--Ti--Mg, and the magnetic films 44
and 23, the conductive nonmagnetic film 7, the Co--Pt film 19 and
the protection film 8 which are the same as the respective
components shown in part (b) of FIG. 23 of the above-mentioned
sixth embodiment are formed on the conductive film 6. In the
magnetic sensor 9G of the present embodiment, a main direct current
bias magnetic field is given by the Co--Pt film 19 of permanent
magnet. In the case that the magnitude of the direct current bias
magnetic field caused by the Co--Pt film 19 is not an optimum
value, the direct current bias magnetic field is finely adjusted by
passing a direct current through the conductive film 6. The direct
current flowing through the conductive film 6 is a minute current;
the power consumption, therefore, is relatively low.
[0110] When the magnitude of the direct current bias magnetic field
caused by the permanent magnet of the Co--Pt film 19 is larger than
the optimum value, the direction of the direct current flowing
through the conductive film 6 is given so as to cancel the magnetic
field caused by the permanent magnet. On the contrary, when the
magnitude of the direct current bias magnetic field caused by the
permanent magnet is smaller than the optimum value, the direction
of the direct current of the above-mentioned conductive film 6 is
reversed so that the direct current bias magnetic field is added to
the magnetic field of the permanent magnet. In this manner, by
selecting the direction and the current value of the direct current
of the conductive film 6, the optimum direct current bias magnetic
field can be generated. Since the conductive film 6 is formed on a
flat surface of the nonmagnetic substrate 1, the surface of the
conductive film 6 also becomes flat. Therefore, there is no
particular problem about the flatness of the respective components
formed on the conductive film 6 in the subsequent process.
Accordingly, the magnetic sensor with high sensitivity and capable
of carrying out a stable measurement can be easily obtained.
EIGHTH EMBODIMENT
[0111] A magnetic sensor 9H of the eighth embodiment in the present
invention is described with reference to FIG. 26 to FIG. 32.
[0112] FIG. 26 is a plan view of the magnetic sensor 9H of the
eighth embodiment in the present invention, and FIG. 27 is a plan
view showing only a soft magnetic film 29 in FIG. 26. The soft
magnetic film 29 has a plurality of parallel and narrow slits 32.
Strip-shaped soft magnetic films 53 interposed between adjacent two
slits 32 and strip-shaped soft magnetic films 54 at upper end and
lower end are formed by providing a plurality of slits 32 on the
plate-shaped soft magnetic film 29. The strip-shaped soft magnetic
films 53 and 54 correspond to the soft magnetic films 23 or 44 in
the above-mentioned second embodiment to seventh embodiment. The
easy axis of magnetization of the soft magnetic film 29 is oriented
to the direction shown by arrow 80 which is perpendicular to the
longitudinal direction of the slit 32 and is along with the film
face.
[0113] Problems of the soft magnetic films 23 and 44 which are
provided on the magnetic sensor of the above-mentioned second
embodiment to seventh embodiment are described below.
[0114] The inventors found that, when a plurality of strip-shaped
soft magnetic films 44, 23 shown in FIG. 24 are placed in the
external magnetic field, for example, the magnetic flux caused by
the external magnetic field concentrates on outer soft magnetic
films 44 shown by arrow 44A (hereinafter is referred to as soft
magnetic film 44A), and the magnetic flux density of the soft
magnetic films 44A becomes higher than the magnetic flux density of
the inner soft magnetic films 44.
[0115] FIG. 28 shows an example of five strip-shaped soft magnetic
films 33 to 37 which are parallel arranged for describing the
concentration of the flux. Referring to the figure, when the soft
magnetic films 33 to 37 are placed in the external magnetic field
Hex 16, magnetic fluxes 31 in the range of a width G of the soft
magnetic films 33 to 37 perpendicular to the direction of the
external magnetic field Hex 16 straightly enter at the left ends
the soft magnetic films 33 to 37, and go out from the right ends.
Magnetic fluxes 28 and 30 which are out of the width G in the
external magnetic field Hex 16 are attracted by the soft magnetic
films 33 and 37 having a high-permeability, and enter the left ends
of the soft magnetic films 33 and 37, and go out from the right
ends. Therefore, the magnetic flux densities of the soft magnetic
films 33 and 37 become larger than the magnetic flux densities of
the soft magnetic films 34 to 36 by the external magnetic field Hex
16.
[0116] FIG. 29 is a graph showing the relation between the external
magnetic field Hex 16 and a magnetic flux density B passing through
the soft magnetic films 33 to 37. The magnetic flux density is a
measurement value at a center part shown by a dash-dot line C of
each of the soft magnetic films 33 to 37. In the figure, a curve 45
shows the magnetic flux density of the soft magnetic films 33 and
37. A curve 47 shows the magnetic flux density of the soft magnetic
films 34 to 36. A curve 46 shows an average magnetic flux density
of the soft magnetic films 33 to 37. In the change of the magnetic
flux density in increase of the external magnetic field Hex from
zero, the curve 45 rises more steeply than the curve 47 does.
Consequently, as shown in FIG. 28, it is proved that the magnetic
fluxes 28 and 30 enter the soft magnetic films 33 and 37. FIG. 30
is a graph showing the characteristics of impedance of the soft
magnetic film having a magnetic flux density characteristic shown
by the curves 45, 46 and 47 in FIG. 29. In FIG. 30, a curve 48
shows the change of impedance Z of the conductive nonmagnetic film
7 due to the magnetic flux passing through the outer soft magnetic
films 33 and 37 in FIG. 28. A curve 49 shows the change of
impedance Z of the conductive nonmagnetic film 7 due to the
magnetic flux passing through the inner soft magnetic films 34 to
36. A curve 50 shows the change of impedance Z of the conductive
nonmagnetic film 7 due to the magnetic flux averaging the magnetic
flux densities of the soft magnetic films 33 to 37. As is realized
from FIG. 30, concerning the soft magnetic film which is a main
element of the magnetic sensor, as shown in FIG. 29, even if the
magnetic flux densities of the outer soft magnetic films 33 and 37
are high, when the magnetic flux densities of a lot of inner soft
magnetic films 34 to 36 are low, improvement of the characteristics
of the magnetic sensor is not realized. In order to improve the
characteristics of the magnetic sensor, it is desirable that the
curve 46 showing the average magnetic flux density in FIG. 29 is
steep. For this purposes, it is required to uniform the magnetic
flux densities of all of the soft magnetic films 33 to 37 shown in
FIG. 28.
[0117] FIG. 31 is a plan view of a soft magnetic film 29A of which
the soft magnetic films 33 to 37 shown in FIG. 28 are connected by
soft magnetic films 51A at right and left ends. By providing the
soft magnetic films 51A at both end parts, the magnetic fluxes 28
and 30 which are out of the range of the width G enter each the
soft magnetic films 33 to 37 through the soft magnetic films 51A.
The inventors found that the magnetic flux densities of each of the
soft magnetic films 33 to 37 become relatively uniform as a result
of the above.
[0118] Concerning the soft magnetic film 29 shown in FIG. 27 which
is provided in the magnetic sensor of the present embodiment,
measurement is carried out as to the densities of the magnetic
fluxes passing through the strip-shaped soft magnetic films 53 and
54 due to the external magnetic field Hex. A side-to side length LA
of the soft magnetic film 29 is 1 mm. The width W8 of the slit 32
is 10 .mu.m, and the widths W9 of the strip-shaped soft magnetic
films 53 and 54 are 40 .mu.m. In the case that a distance S from
the right and left ends of the soft magnetic film 29 to the ends of
the slit 32 is set to 25 .mu.m, 50 .mu.m, 100 .mu.m and 200 .mu.m,
the densities of the magnetic fluxes passing through each of the
strip-shaped soft magnetic films 53 and 54 are measured at the
center part shown by a dash-dot line C, and the result is shown in
FIG. 32. In FIG. 32, the ordinate designates magnetic flux density
B. The abscissa designates the number of strip-shaped soft magnetic
films 53 and 54 allotted in the order from the lower one to the
upper one. Numeral "1" shows the lowest strip-shaped soft magnetic
film 54. Numeral "2" shows the second strip-shaped soft magnetic
film 53 from the bottom. Numeral "10" shows the uppermost
strip-shaped soft magnetic film 54. Hereafter, the strip-shaped
soft magnetic films from the numeral "1" to "10" are called as the
strip-shaped soft magnetic films of number 1 to number 10,
respectively.
[0119] In FIG. 32, a curve 61 shows a magnetic flux density
distribution when S is zero, in other words, the soft magnetic
films 51 are not disposed at the ends. According to the curve 61,
the magnetic flux densities of the strip-shaped soft magnetic films
54 of number 1 and number 10 are extremely large such as 4.0, and
the magnetic flux densities of the strip-shaped soft magnetic films
53 from number 3 to number 8 are low such as about 1.0. A curve 62
shows a magnetic flux density distribution when S is 25 .mu.m. In
this case, the magnetic flux densities of the strip-shaped soft
magnetic films 54 of number 1 and number 10 lower to 2.5, and the
magnetic flux densities of the strip-shaped soft magnetic films 53
of number 3 to number 8 rise to about 1.4. A curve 64 shows a
measurement result similar to the above when S is 100 .mu.m, and
the magnetic flux densities of the strip-shaped soft magnetic films
54 of number 1 and number 10 further lower, on the other hand, the
magnetic flux densities of the strip-shaped soft magnetic films 55
of number 3 to number 8 further rise. By the above-mentioned
measurement result, it is found that the magnetic flux density
distribution of the soft magnetic films 53 and 54 can be made
fairly uniform by setting S from 100 to 200 .mu.m.
[0120] According to the present embodiment, the densities of the
magnetic flux passing through the strip-shaped soft magnetic films
53 and 54 due to the external magnetic field Hex can be made
approximately uniform. As a result, the impedance change, of the
conductive nonmagnetic film 7 with respect to the external magnetic
field Hex becomes large, and the detection sensitivity of magnetism
is improved. The sensitivity of the magnetic sensor in each
embodiment can be further improved by using the soft magnetic film
29 of the structure shown in FIG. 27 instead of the soft magnetic
films 23 and 44 in the above-mentioned second to seventh
embodiments.
[0121] In each embodiment mentioned above, the material of the
nonmagnetic substrate 1 is preferably a ceramic of the group of
Ni--Ti--Mg, but a material of group of nonmagnetic ferrite such as
NiZn, a nonmagnetic material such as glass or various ceramic may
be used.
[0122] The material of the soft magnetic films 4, 44 and 29 is
preferably FeTaN, but an alloy such as NiFe, FeCo and FeN may be
used. The soft magnetic film is preferably soft magnetic material
having a high permeability such as an amorphous alloy (an alloy
including Co as a main component, for example, CoNbZr, CoTaZr,
CoSiB, an alloy including Fe as a main component such as a FeSiB)
or a nanno-crystal alloy (such as FeTaN including Fe as a main
component) and an alloy of the group of NiFe. The material of the
insulation film 5 is preferably SiO.sub.2, but inorganic material
such as alumina, glass, or organic insulation film such as
polyimide resin may be used. NiZn ferrite magnetic film may be used
for the insulation film 21 instead of SiO.sub.2 in the second
embodiment. For the material of a permanent magnet, a film of
Co--Pt is suitable, but permanent magnet materials such as the
group of ferrite, the group of Nb, and the group of Co may be used.
For the material of the conductive nonmagnetic film, copper is
suitable, but conductive metals such as Au, Ag and Cr may be used.
The permanent magnet for applying the direct current bias magnetic
field is not limited to be placed at the positions shown in the
above-mentioned embodiments, but it may be placed at any position
at which the direct current magnetic field can be applied to the
soft magnetic film. For the material of the protection layer 8,
SiO.sub.2 is suitable, but alumina or some other inorganic
materials or ceramics may be used. The thickness of the protection
layer was 1 .mu.m, but it is desirable that its thickness is made
thin to about 0.1 .mu.m in order to reduce power consumption of the
direct current power source for applying the direct current
magnetic bias.
NINTH EMBODIMENT
[0123] A magnetic sensor 9I of the ninth embodiment in the present
invention is described with reference to FIG. 33 and FIG. 34. FIG.
33 is a perspective view of the magnetic sensor 9I of the ninth
embodiment, and FIG. 34 is a plan view thereof. As shown in FIG. 33
and FIG. 34, a first soft magnetic film 73 of a strip-shaped film
which is preferably Fe--Ta--N is formed on the face of a
nonmagnetic substrate 1 which is preferably Ni--Ti--Mg. In FIG. 33,
two soft magnetic films 73 are provided in parallel with
predetermined intervals, but the number of the soft magnetic film
73 is not limited to two, and may be set to an arbitrary
number.
[0124] An insulation layer 75 of SiO.sub.2 is provided on a part of
the soft magnetic film 73. In FIG. 33, two insulation layers 75 are
provided on one soft magnetic film 73, the number of the insulation
layer 75 is not limited to two, and may be set to an arbitrary
number. In the figure, a conductive film 76A and a conductive
nonmagnetic film 77A which are separated from each other in upper
and lower directions are provided so as to pass through an
insulation layer 75 of front side. Preferably, the conductive
nonmagnetic films 76A and 77A are made of copper (Cu). Moreover, a
conductive film 76B and a conductive nonmagnetic film 77B which are
separated from each other are provided so as to pass through an
insulation layer 75 of back side. A second soft magnetic film 74
which is preferably a film of Fe--Ta--N is provided on the
insulation layer 75 and the soft magnetic film 73 having no
insulation film thereon. A closed magnetic path M is formed with
the soft magnetic films 73 and 74. In the case that the soft
magnetic films 73 and 74 have a magnetic anisotropy, it is
preferable that the respective easy axes of magnetization are in
the direction perpendicular to the longitudinal direction of the
soft magnetic films 73 and 74 and along with the film face. The
left ends of the conductive nonmagnetic films 77A and 77B in the
figure are connected with each other by a connection conductor 78.
The right end of the conductive nonmagnetic film 77A is connected
to a terminal 81A through a connection conductor 79A. The right end
of the conductive nonmagnetic film 77B is connected to a terminal
81B through a connection conductor 79B. With this configuration,
the conductive nonmagnetic films 77A and 77B of meander type are
formed.
[0125] The right end of the conductive film 76A is connected to a
terminal 84A through a connection conductor 83A. The left end of
the conductive film 76A is connected to the right end of the
conductive film 76B through the connection conductor 83B. The left
end of the conductive film 76B is connected to a terminal 84B
through a connection conductor 86. In the above-mentioned
configuration, the conductive films 76A and 76B, as well as the
conductive nonmagnetic films 77A and 77B are included in the closed
magnetic path which are formed of the soft magnetic film 73 and the
soft magnetic film 74, and the connection conductors 83A and 83B
are outside of the closed magnetic path.
[0126] In FIG. 33, the conductive nonmagnetic films 76A, 76B, 77A,
77B and the connection conductors 83A and 83B appear to float above
the nonmagnetic substrate 1, but in the actual configuration,
insulation layers omitted in drawing are provided between each of
the conductive nonmagnetic films and each of the connection
conductors.
[0127] Operation of the magnetic sensor 9I of the present
embodiment is described below. As shown in FIG. 34, a direct
current power source 10 is connected across the terminals 84A and
84B, and a direct current is passed through the conductive
nonmagnetic films 76A and 76B in the direction shown by arrow 88.
By this direct current, a direct current bias magnetic field is
applied to the soft magnetic films 73 and 74. A high frequency
power source 11 of a constant current is connected across the
terminals 81A and 81B through a resistor 12, and a high frequency
current of 10 MHz for example is passed. A high frequency amplifier
13 is also connected across the terminals 81A and 81B.
[0128] When the magnetic sensor 9I of the present embodiment is
placed in the external magnetic field Hex 16 of such as
geomagnetism, the impedances of the conductive nonmagnetic films
77A and 77B vary due to the magneto-impedance effect. The variation
of the high frequency voltage generated across the terminals 81A
and 81B due to this impedance variation is detected by amplifying
and detecting by the high-frequency amplifier 13, thereby an
extremely small external magnetic field Hex 16 of the order of 0.3
Oe (24 A/m) can be detected.
[0129] In the magnetic sensor 9I of the present embodiment, since
the conductive films 76A and 76B for applying the direct current
bias magnetic field are provided in the closed magnetic path M
which are formed by the soft magnetic films 73 and 74, a
sufficiently large direct current bias magnetic field can be
generated by passing a relatively small direct current. Although it
is required to pass a direct current of 30 mA or more through the
conductive film 6 in the magnetic sensors 9-9H in the
above-mentioned embodiments, a sufficient direct current bias
magnetic field can be obtained by passing a current of 10-20 mA
through the conductive nonmagnetic films 76A and 76B in the
magnetic sensor 9I of the present embodiment.
[0130] In order to prove this matter, inventors performed an
experiment which is described below with reference to FIG. 41.
[0131] Part (a) and part (b) of FIG. 41 are cross-sectional views
of a magnetic sensor which is made for the experiment. In part (a)
of FIG. 41, a conductive body 98 is formed between soft
magnetic-bodies 96 and 97 at a center part with an insulation film
therebetween. A direct current is passed through the conductive
body 98 in the direction perpendicular to the paper face as shown
by a dot in a circle and a cross in a circle, and a magnetic field
is generated, and a magnetic flux density is measured at a position
A1 of the lower yoke 96. In part (b) of FIG. 41, conductive bodies
99A and 99B are placed at center upper and lower parts of the
magnetic sensor having the same configuration as that of part (a)
of FIG. 41. A direct current is passed-through the conductive
bodies 99A and 99B in the directions which are perpendicular to the
paper face and are inverse with each other. The direct current is
not passed through the conductive body 98. In a manner similar to
part (a) of FIG. 41, a magnetic flux density at a position A2 of
the lower yoke 96 in part (b) of FIG. 41 is measured. When the same
value of direct current is passed through the conductive body 98 in
part (a) of FIG. 41 and the conductive bodies 99A and 99B in part
(b) of FIG. 41, the magnetic flux density at the position A1 in
part (a) of FIG. 41 is about 80 times the magnetic flux density at
the position A2 in part (b) of FIG. 41.
[0132] From the above-mentioned experimental result, in the case
that the conductive body 93 which passes the direct current is
placed in the closed magnetic path which is formed by the lower
yoke 96 and the upper yoke 97 as shown in part (a) of FIG. 41, a
large direct current bias magnetic field can be obtained by a
smaller direct current in comparison with the case that the
conductive bodies 99A and 99B are placed outside of the closed
magnetic path as shown in part (b) of FIG. 41.
[0133] The fabrication method of the magnetic sensor 9I of the
ninth embodiment is described with reference to FIG. 35 and FIG.
36. Part (d) of FIG. 35 is a cross-sectional view taken along the
line XXXV-XXXV in FIG. 34, and part (a)-part (c) are
cross-sectional views in each process to part (d) of the
same-figure. Part (d) of FIG. 36 is a cross-sectional view taken
along the line XXXVI-XXXVI in FIG. 34, and part (a)-part (c) are
cross-sectional views in each process to part (d) of the same
figure. Part (a) through part (d) of FIG. 36 are cross-sectional
views in the same processes as the processes which are shown in
part (a) through part (d) of FIG. 35, respectively. In other words,
part (a) of FIG. 35 and part (a) of FIG. 36 are cross-sectional
views at different places in the same process, and part (b)-part
(d) of FIG. 35 and part (b)-part (d) of FIG. 36 are made likewise.
In FIG. 35 and FIG. 36, in order to enhance ease of understanding
of the figures, hatchings are applied only a part of cross
sections.
[0134] In part (a) of FIG. 35, a strip-shaped first soft magnetic
film 73 of 1.0 .mu.m thick is formed on an upper face of the
nonmagnetic substrate 1 of a ceramic of the group of Ni--Ti--Mg by
sputtering of Fe--Ta--N, and subsequently is formed in a pattern
having a predetermined shape. The first soft magnetic film 73 may
be formed on the surface of the substrate 1 with an insulation
material therebetween. Subsequently, an insulation film 91 is
formed on an entire face of the substrate 1 including the soft
magnetic film 73 by sputtering of SiO.sub.2 (Low temperature
magnetron sputtering is preferable.) or vapor deposition.
[0135] The cross section taken along the line XXXVI-XXXVI after
completion of the process in part (a) of FIG. 35 is shown in part
(a) of FIG. 36. As shown in part (a) of FIG. 36, two soft magnetic
films 73 are provided in parallel to each other on the face of the
substrate 1 and are covered with the insulation film 91.
[0136] In part (b) of FIG. 35, conductive films 76A and 76B of 1.0
.mu.m thick are formed by sputtering of copper (Cu) on the
insulation film 91, and subsequently are formed in a pattern having
a predetermined shape. After an insulation film 92 is formed on an
entire face of the substrate 1 including the conductive films 76A
and 76B, conductive nonmagnetic films 77A and 77B are formed
respectively on the positions overlapping the above-mentioned
conductive films 76A and 76B on the insulation film 92.
[0137] In this process, as shown in part (b) of FIG. 36, connection
parts 89B and 89C are formed on the insulation film 91, and a
connection conductor 78 is formed on the insulation film 92. Where,
the conductive films 76A and 76B and the connection parts 89B and
89C may be formed in the same process with the same material.
Furthermore, the conductive nonmagnetic films 77A and 77B and the
connection conductor 78 may be formed in the same process with the
same material.
[0138] In part (c) of FIG. 35, an insulation film 93 is formed on
the conductive nonmagnetic films 77A and 77B. Subsequently, the
insulation films 91 and 92 placed on the soft magnetic film 73 are
removed so that the insulation films 91 and 92 placed on the
conductive nonmagnetic films 77A and 77B and adjacent thereto
remain. Then, a second soft magnetic film 74 is formed on the soft
magnetic film 73 including the insulation film 93.
[0139] A cross-section taken along the line XXXVI-XXXVI after
completion of this process is shown in part (c) of FIG. 36. As
shown in part (c) of FIG. 36, the first soft magnetic film 73
contacts the second soft magnetic film 74. In part (d) of FIG. 35,
an insulation film 94 is formed on an entire face including the
second soft magnetic film 74. Subsequently, as shown in part (d) of
FIG. 36, the insulation films 92, 93, 94 placed on the connection
parts 89B and 89C are removed by etching and through holes are
formed, and the connection parts 89B and 89C are exposed. Then,
connection conductor 83B connected to the connection parts 89B and
89C at the respective ends is formed on the insulation film 94. The
connection parts 89B and 89C are electrically connected by the
connection conductor 83B. A connection part 89 between the
conductive film 76A and the connection conductor 83A and a
connection part 89A between the connection conductor 83A and the
terminal 84A are connected in a similar manner mentioned above.
TENTH EMBODIMENT
[0140] A magnetic sensor 9J of the tenth embodiment of the present
invention is described with reference to FIG. 37 and FIG. 38. FIG.
37 is a perspective view of a relevant part of the magnetic sensor
9J of the tenth embodiment. FIG. 38 is a plan view of the magnetic
sensor 9J of the present embodiment.
[0141] Referring to FIG. 37, in the magnetic sensor 9J of the
present embodiment, the conductive film 76A and the conductive
nonmagnetic film 77A which penetrate through the insulation film 75
provided between the soft magnetic films 73 and 74 are placed
substantially on the same plane so as to be separated from each
other. In a similar manner, the conductive film 76B and the
conductive nonmagnetic film 77B are placed substantially on the
same plane so as to penetrate through the insulation layer 75. The
remaining configurations are the same as those of the magnetic
sensor 9I of the above-mentioned ninth embodiment. As shown in FIG.
36, the method of connecting the direct current source 10, the high
frequency source 11 and the high frequency amplifier 13 which are
connected during operation of the magnetic sensor 9J is similar to
the case of the magnetic sensor 9I and the operation is also
similar.
[0142] According to the present embodiment, since the conductive
film 76A, the conductive nonmagnetic film 77A are provided
substantially on the same plane in the insulation layer 75, the
height of a top part 74B of the soft magnetic film 74 from the face
of the substrate 1 becomes lower than the magnetic sensor 9I of the
above-mentioned ninth embodiment. Furthermore, apart from the
magnetic sensor 9I of the ninth embodiment wherein the conductive
film 76A and the conductive nonmagnetic film 77A must be formed in
layers through separate processes, in the case of magnetic sensor
9J of the tenth embodiment, the conductive film 76A and the
conductive nonmagnetic film 77A can be formed in one same process
and with the same material, such as the nonconductive nonmagnetic
film. Therefore, the fabrication process becomes simple, and the
fabrication cost is also reduced. Furthermore, in the case that the
conductive film 76A and the conductive nonmagnetic film 77A are
layered as the magnetic sensor 9I of the ninth embodiment, there is
a possibility that a shortcircuiting may occur due to dust or the
like entering between them in the fabrication processes; however,
in the magnetic sensor 9J of the tenth embodiment, the fear of the
shortcircuiting is greatly reduced. As a result, a yield rate in
the fabrication is improved, and yields are improved.
[0143] Fabrication method of the magnetic sensor 9J of the tenth
embodiment is described with reference to FIG. 39 and FIG. 40. Part
(d) of FIG. 39 is a cross-sectional view taken along the line
XXXIX-XXXIX in FIG. 38, and part (b) through part (d) are
cross-sectional views in the respective processes. Part (d) of FIG.
40 is a cross-sectional view taken along the line XXXX-XXXX in FIG.
38, and part (b) through part (d) are cross-sectional views in the
respective processes. Parts (a) through (d) of FIG. 40 are
cross-sectional views in the same processes as the respective
processes shown by parts (a) through (d) of FIG. 39. In other
words, part (a) of FIG. 39 and part (a) of FIG. 40 are
cross-sectional views at different parts in the same process, and
parts (b) through (d) of FIG. 39 and parts (b) through (d) of FIG.
40 are shown in a similar manner. In FIG. 39 and FIG. 40, cross
sections are only partially hatched for making the figures easy to
see.
[0144] In part (a) of FIG. 39, the soft magnetic film 73 of 1.0
.mu.m thick which forms a lower yoke is formed on the face-of the
nonmagnetic substrate 1 such as a ceramic of Ni--Ti--Mg group by a
sputtering of Fe--Ta--N, and then carried out a pattern formation
into a predetermined shape. Subsequently, the insulation film 91 is
formed on an entire face of the substrate 1 including the soft
magnetic film 73 by a sputtering of SiO.sub.2. The cross section
taken along the line XXXX-XXXX after the completion of this process
is shown in part (a) of FIG. 40.
[0145] In part (b) of FIG. 39, conductive nonmagnetic films 76A,
77A, 76B and 77B are formed by a-sputtering of Cu on the insulation
film 91, and then carried out a pattern formation into a
predetermined shape. Moreover, as shown in part (b) of FIG. 40,
connection conductors 78 and 89C are formed on the insulation film
91. The conductive nonmagnetic films 76A, 77A, 76B, 77B and the
connection conductors 78, 89C may be formed in the same process
with the same material, and on the entire face of the substrate 1
including these, the insulation film 92 of SiO.sub.2 is formed. A
cross section taken along the line XXXX-XXXX after the completion
of this process is shown in part (b) of FIG. 40.
[0146] In part (c) of FIG. 39, the insulation films 91 and 92 on
the soft magnetic film 73 are removed except for the vicinity of
the conductive nonmagnetic films 76A, 77A, 76B and 77B, and the
soft magnetic film 73 is exposed. A soft magnetic film 74 is formed
on the insulation film 92 remaining on the conductive nonmagnetic
films 76A, 77A, 76B and 77B and on the exposed soft magnetic film
73 by a sputtering of Fe--Ta--N, and then a pattern of a
predetermined shape is formed. The cross section taken along the
XXXX-XXXX line after the completion of this process is shown in
part (c) of FIG. 40.
[0147] In part (d) of FIG. 39, the insulation film 93 of SiO.sub.2
is formed on an entire face including the soft magnetic film 74 on
the substrate 1. Subsequently, the insulation film 92 on the
connection conductor 89C is removed and through holes are formed.
The connection conductors 83A and 83B are formed on the insulation
film 93. By this process, as shown in part (d) of FIG. 40, the
conductive nonmagnetic film 76B and the connection conductor 83B
are electrically connected at the connection part 89C. Connections
at the connection parts 83C, 83D and 84D are carried out by the
same process as the connection part 89C. The magnetic sensor 9J of
the present embodiment is fabricated by the above-mentioned
processes.
[0148] In the above-mentioned ninth and tenth embodiments, a
ceramic (Ni--Ti--Mg) containing nickel oxide NiO, titanium oxide
TiO.sub.2 and magnesium oxide MgO, a ceramic (Ti--Ca) containing
titanium oxide and calcium oxide CaO, and a ceramic (AlTiC)
containing aluminum oxide Al.sub.2O.sub.3 and titanium carbide TiC,
glass, silicon or the like can be used for the nonmagnetic
substrate 1. The roughness of the surface of the nonmagnetic
substrate is preferably Ra5 nm or below in order to keep a large
coercive force Hc.
[0149] The soft magnetic films 73, 74 are preferably a soft
magnetic material having a high permeability such as an amorphous
alloy (an alloy containing Co as a main component, for example
CoNbZr, CoTaZr, CoSiB, or an alloy containing Fe as a main
component, for example FeSiB or the like), or a nanno-crystal alloy
(FeTaN or the like containing Fe as a main component) and such as
an alloy of the group of NiFe.
[0150] It is preferable to achieve 1000 or more of permeability at
10-20 MHz of frequency.
[0151] The insulation films 91-94 are preferred to be an oxide such
as SiO.sub.2, Al.sub.2O.sub.3, or an organic insulation film such
as a polyimide resin.
[0152] Gold (Au), silver (Ag), copper (Cu) or the like are usable
for the conductive nonmagnetic films and the connection wires. It
is preferable to form a thin film of 30 nm-100 nm thick of Cr, Ta
or Ti to improve adherence between the film of Au, Ag, Cu or the
like and the insulation film.
[0153] Industrial Applicability
[0154] As described in detail in the above-mentioned embodiments,
in the magnetic sensors of the present invention, a soft magnetic
film having an easy axis of magnetization in a predetermined
direction is opposed to a zigzag conductive nonmagnetic film of
meander type with an insulation film therebetween, and moreover, a
conductive film is provided on the conductive nonmagnetic film with
an insulation film therebetween. A high frequency current is passed
through the conductive nonmagnetic film of meander type, and a
direct current bias magnetic field is applied. When an external
magnetic field is applied to the magnetic sensor, a conductor
having a long path of the conductive nonmagnetic film of meander
type parallel to the easy axis of magnetization receives a magnetic
action of the soft magnetic film, and even in the case that a high
frequency current of a relatively low frequency is passed, an
impedance greatly changes. The external magnetic field can be
detected with a high sensitivity by detecting the impedance
change.
* * * * *